Installing DBA 2657 rotors in the rear

[fletch]

Here is my experience in mounting the DBA 2657 rotors to the rear hubs. The purpose of which is to create a near "square" brake setup to match the weight distribution to the 818 while also retaining the Subaru parking brakes.

Items required:
Subaru rear wheel housings & hubs
Forester XT rear backing plates - I'm using DORMAN P/N MTM 924-375 from RockAuto
Forester XT front calipers, brackets, & bolts
Rear bearings & seals
DBA 2657 rotors
Angle grinder
Drill & dremel or milling machine

This post was very helpful in sorting out a variety of compatibility issues. https://forums.nasioc.com/forums/sho....php?t=1265631


The steps are generally this:
1) Disassemble donor rear housing. Press out the hubs to remove the rear backing plates. I had parts from an 05 Forester XT and could have used the backing plates, but I made two mistakes which I'll point out below. So, if you've got OEM plates feel free to use them. If not, buy the DORMAN parts. Note: The important part here is the spacing of the holes for the caliper carrier.
New_BP.JPG

2) Modify the backing plates and caliper carriers to fit one another. The backing plates need to have the dust shields removed and holes widened/relocated for the caliper bolts. Work to make the holes equidistant from the center of the inner circle. They also need some trimming of the parking break carrier area. <--- This is where I made one of my errors with the OEM plates. **** The six "lands" on the parking brake support area need to be preserved in their entirety. Don't trim them at all. They need to be in place to support the parking brake shoes through their full range of motion. You can see the lands in the 4th picture below. ****
The caliper carriers need to have some material cut out of the back side. The caliper bolts will also need some sort of spacers to keep them from poking through the carriers into the rotors. I used various drill sizes working up to 1/2" for the holes. The "snowman" hole was a real pain, but I made do with a variety of dremel bits and a dose of patience. In the third picture, note the material removed from the bottom edge of the caliper carrier.
Prepped_BP.JPG
Brkt_Mod1.JPG
Brkt_Mod2.JPG
ParkBrake.JPG

3) Once you've got a good fit between the backing plate and the carrier, press the hubs & bearings together.
Caliper_Install1.JPG
CaliperInstall2.JPG

4) The rotor hats will need to have ~1/4" of radius removed from them in order to clear the caliper carriers. So, make friends with a machinist. This step along could cost more than all the rest.
RotorInstall.JPG

I've gotten this far and found I've got a small clearance problem between the rear face of the rotor and the caliper carrier. There is a small interference so I'll need to grind a small amount from the inner face of the carrier to allow the rotor to spin freely.

More to come...

Oh yeah, my second mistake. I don't have any idea how I did this, but I ended up warping one of the OEM backing plates. When I bolted it to the wheel housing I discovered it was potato-chipped such that the plane of the caliper bolt holes was not coplanar with the hub surface. Again, I don't know how I managed to do this, but I clearly wasn't going to use a crooked backing plate.

[fletch]

The caliper carriers required some additional love from the grinder & dremel on the inside surface where the back side of the rotor interfered. In the third picture above, you can see the half-moon shaped bosses near the bolt holes. There were several other bosses hidden by the "hoop" in that picture that needed to be ground down. Clearance is tight, but it worked. Brakes are fully mounted to the car now and there is no contact.

One final modification was needed. The inner brake pads needed a spacer to make up for the narrow-than-factory rotors (20 mm DBA vs. 24 mm Subaru). I really only needed 3/16", but had 1/4" steel available. So we welded some spacers to the rear side of the inner brake pads, similar to Bob_n_Cincy's approach of welding old backing plates to the inner pads.

After installing the front & rear suspension and brakes we were excited to put some wheels on and drop it off the jackstands even just for a short photo-op. Alas, none of the wheels we have fit over the brakes. We'll need to figure out what wheels work at some future date.

[grathke]

Thanks Fletch for such a great write up.

I'm starting mine this weekend, thanks to you, Bob from Cincinnati, and Jamie from Ohio.

First thing I noticed at the beginning of my project, you do not need to remove the backing plate to remove the dust shield. I used a tin snip and cut off the raised portion around the shield, 5 minutes perhaps. I then took a cold chisel and pried the remaining portion off from the spot welds, perhaps 5 minutes too. All in all took about 15 minutes to taje that off and get it cleaned up where it doesn't even look like it had a dust shield.

Glenn

[grathke]

Thanks to everyone who has contributed to the rear brake modifications. Sure made it an easy go for me.

Special shout out to Bob, Jamie, and Fletch.

Here is my finished look. Almost forgot to mention, I used EBC GreenStuff front and rear, and it stops nicely without being broken in.

2020-09-12 08.39.59-1.jpg

Glenn

[Bob_n_Cincy]

Thanks to everyone who has contributed to the rear brake modifications. Sure made it an easy go for me.

Special shout out to Bob, Jamie, and Fletch.

Here is my finished look. Almost forgot to mention, I used EBC GreenStuff front and rear, and it stops nicely without being broken in.

2020-09-12 08.39.59-1.jpg

Glenn

Glen, Looks great, I've got the same picture. I took a little more of the diameter off the e-brake housing. I'm sure you will be happy with the braking performance.
Bob bb.jpg